This invention relates to an appliance for personal use such as a toothbrush, an oral irrigator, a shaver, or a kitchen machine, with an electric motor and a control stage for the electric motor""s energy supply.
Appliances of this type are in widespread use, the known appliances including, for example, appliances for personal use such as electric toothbrushes, electric oral irrigators, electric shavers, and electric household and kitchen appliances or the like. Further known appliances of this type include office communication machines, electrically powered toys or the like. However, the present invention is not restricted in its application to the appliances mentioned but can be used in principle on any appliance that has an electric motor. In many cases there is a need to send information to the users of such appliances. For the transmission of information, the appliances often have separate built-in sound transmitters, light transmitters or some other transmitters of information; for example, toothbrushes are already known that have a type of loudspeaker as a transmitter of information, thus enabling the user to be informed, for instance, about the elapsed brushing time or similar time intervals. These sound transmitters can be constructed as dynamic, electrostatic, magnetostatic or piezo loudspeakers.
The disadvantage of the known appliances is, however, that an additional sound transmitter is required for an acoustic information transfer, which not only increases the manufacturing cost of the appliance but also takes up considerable space in the appliances. Further more, particularly with hermetically encapsulated appliances such as appliances with watertight housings, there is the problem of having to introduce measures that allow the sound waves generated in the interior of the appliance to reach the user.
An object of the present invention is to further develop an appliance with the features initially referred to such that it is possible, in an extremely simple and economical manner, to generate information signals, in particular user-perceptible, preferably audible signals.
During off-periods of the electric motor the control stage supplies the electric motor with energy. This energy has specific terms of duration and/or amplitude, and when the electric motor is off and is in its capacity as an electroacoustic transducer, this energy emits at least in part in the form of audible signals.
The use of an electric motor as a sound transmitter or electroacoustic transducer when off obviates the need to provide additional, separate components such as loudspeakers or the like. The electric motor, which is present in any case for drive purposes, can be operated during off-periods as an electroacoustic transducer under suitable control from the control stage. Furthermore, the electric motor used in the appliance is mechanically connected to the appliance or the appliance housing. Thus, sound is emitted readily via this connection from the interior of the appliance through the appliance or appliance housing to the environment, and in a volume easily perceived by the user. When the electric motor is off and not called on to supply any mechanical drive energy, the electric motor is suitably controlled to operate as a sound transmitter or loudspeaker. Electric motors here are understood to be a means for converting electric energy into mechanical energy, for example drive energy.
It is an advantage for the electric motor to be constructed as a low-duty motor, for example, as a direct-current motor comprising a rotor and a stator. The invention is not restricted, however, to such motors but can also find application, individually adapted in accordance with the given conditions, in asynchronous, synchronous, stepping and reluctance motors.
In some embodiments, the control stage feeds analog signals to the electric motor. In these embodiments, the analog signal, for example a voltage signal, contains the spectrum of the audible signals to be emitted by the electric motor.
In further embodiments, the analog signal may also contain frequency mixes, for example to generate audible speech or music signals.
Advantageously, the analog signal is a unipolar signal, enabling the electronic components as well as the energy supply, which is, for example, a storage battery or the like, to be constructed with utmost ease.
It is also possible, however, for the analog signal to be a bipolar signal. A bipolar control is slightly more elaborate in its electronic outlay but it enables far higher control amplitudes and hence acoustic power because the average of the bipolar signal is invariably zero.
In a further embodiment of the invention, the control stage feeds digital signals to the electric motor. In this embodiment the digital signals preferably are constructed as pulse-duration-modulated signals and preferably have in particular an essentially constant maximum amplitude.
The fundamental frequency of the digital signal essentially represents the pitch of the audible signal, disregarding the overtones.
It is particularly important for the embodiments of the invention that the time average of the signal lie below a signal threshold value that causes the electric motor to start up.
In this connection it has been shown that the signal threshold value varies in response to the signal frequency and in particular that it rises with the frequency, Hence it is possible to control the electric motor at higher frequencies with higher signal amplitudes, thus resulting in better acoustic power.
The fact that the signal has no frequencies below a frequency threshold value that causes the electric motor to start up is another advantage.
According to a further advantageous aspect of the invention, provision is made for a time delay between the instant the electric motor is shut off as a driving mechanism and the instant it is operated as an electroacoustic transducer.
Advantageously, the electric motor has a brake, for example a mechanical brake with a constant braking torque, or a start-up brake with a braking torque that decreases after the motor starts up.
In various cases of application, it is an advantage for the electric motor to have a device for positioning the rotor in a defined position of rest.
To optimize efficiency in terms of acoustic power output, the electric motor is equipped according to a further embodiment of the invention with an accordingly adapted motor housing or motor housing material.
Provision is made preferably for mechanical elements such as ribs, hard parts or the like between the appliance or appliance housing and the electric motor, which optimize the acoustic emission of the appliance or appliance housing.
The control stage is preferably formed by a driving stage that is connected to the energy supply on one side and to a signal generator on the other side and, where applicable, to additional electronic components.
The appliance of the invention is preferably used as a drive, for example for a toothbrush, an oral irrigator, a shaving system, a household machine, an office machine or the like. Application of the invention is generally not limited to certain types of appliance or appliance applications but is suitable for all appliances that have an electric drive motor and a control device for the electric motor""s energy supply.
Further advantages, features, application possibilities and aspects of the present invention will become apparent from the subsequent description of embodiments. In this context, all features described and/or depicted, whether individually or in any reasonable combination, constitute the object of this invention irrespective of their summary in the claims or the cross references of the latter.